KR100397365B1 - Process Integrating a Solid Oxide Fuel Cell and an Ion Transfer Reactor - Google Patents

Abstract

The present invention delivers the electric force and the generated gas by transporting the solid oxide fuel cell and the oxygen containing gas (typically air) to the first cathode side of the solid oxide fuel cell and the gaseous fuel to the first anode side. At least one ion transfer reactor for generating. Oxygen ions are transferred through the membrane in the fuel cell to the first anode surface and exothermicly react with the gaseous fuel to generate electrical forces and heat. The heat and oxygen transfer is a high temperature reduced oxygen containing gas exiting the cathode side of the solid oxide fuel cell, where a substantial portion of the residual oxygen is delivered to the first ion transfer reactor where it is delivered through an oxygen selective ion transfer membrane. Create a retentate flow of the state and the product gas stream is then recovered.

Description

Process Integrating a Solid Oxide Fuel Cell and an Ion Transfer Reactor

The present invention relates to a process for co-production of power and at least one product gas. More specifically, the process integrates a solid oxide fuel cell and an ion transfer reactor.

Electric forces are traditionally generated by thermodynamic processes. For example, heat can be generated by burning oil in a boiler to superheat pressurized water. The superheated water is expanded by pressurized steam which mechanically rotates the turbine. The rotation of the rotor windings of the rotor of the generator connected to the turbine through a suitable magnetic field generates an electric force.

Conventional electric force generation uses a thermal / mechanical process and its efficiency is limited by the Carnot cycle. The Carnot cycle stipulates that even under abnormal conditions, a significant portion of the thermal energy is released since the heat engine cannot convert all of the supplied thermal energy into mechanical energy. In the Carnot cycle, the engine receives heat energy from a high temperature heat source, converts some of the heat energy into mechanical work and releases the remaining heat energy into a low temperature heat sink. The heat energy released causes a decrease in efficiency.

Another process for generating electricity uses a solid oxide fuel cell. Electric forces are obtained by directly converting energy released by chemical reactions rather than thermal / mechanical processes. As a result, the solid oxide fuel cell is not limited to the efficiency of the Carnot cycle, and the generation of high efficiency electric force is theoretically possible.

Solid fuel cells are disclosed in US Pat. No. 5,413,879 to Domerakii et al. The patent discloses a solid oxide fuel cell having a gas sealed ceramic membrane separating the air chamber from the fuel chamber. Ceramic membranes are typically three layer composites having gas-sealed nucleus portions formed from ceramic membrane materials, such as yttria-stabilize zirconia, which selectively transfer oxygen ions by diffusion. The surface portion of the ceramic film in contact with air is coated with an electrode made of strontium-doped lanthanum manganite doped with strontium. The opposite surface portion of the ceramic membrane in contact with the fuel is a fuel electrode which is a nickel-zirconia cermete. Internal contacts are provided on two electrodes connecting several electrical fuel cells in series or in parallel and recovering the current generated by the ion flux. Suitable solid fuel cells are disclosed in US Pat. Nos. 4,490,444 and 4,728,584 to Eisenberg.

Hot air contacts the air electrode and oxygen is separated from the air by ion transfer through the ceramic membrane to the surface of the fuel electrode. Gaseous fuels (typically light hydrocarbons such as natural gas or carbon monoxide) are in contact with the fuel electrode surfaces and exothermic with oxygen ions to produce electricity and heat as a result of internal energy losses. Hot, partially oxygen depleted gas exits the fuel cell from the cathode or retaining side, and reaction or combustion products exit the fuel cell from the anode or permeate side.

Systems that generate electric forces using solid oxide fuel cells include (1) internal electrical losses at the electrodes, mainly (2) high temperatures in the range of about 700-1000 ° C. where air must be heated, and (3) volume of typically available oxygen. The efficiency achievable is limited because of several factors, including the fact that only a fraction of the oxygen contained in hot air is transferred through the ceramic membrane to react with the gaseous fuel to a level that is approximately 20-30% on the basis. The residual amount of oxygen is released in the holding stream exiting the air chamber. Part of the energy added to the holding and permeate flow is lost as a result of the pressure drop and the limited effectiveness of the additional recuperative heat exchanger.

U.S. Pat.No. 5,413,879 to Domeraki discloses the temperature of the mixture by combining the reaction product from the chemical reaction in the fuel chamber with the hot gas retentate from the air chamber and reacting it with additional fuel in the combustor. Start raising the. The hot mixture heats up the compressed gas used to drive the turbine.

Some types of ion transfer membranes are disclosed in US Pat. No. 5,733,435 to Prasard et al. In the case of membranes exhibiting only ionic conductivity, the outer electrode is placed on the surface of the membrane and current flows back through the outer circuit. In the mixed conductive film, the electrons are internally transferred to the cathode surface, thus completing the circuit and removing the need for the external electrode in advance in a pressure driven mode. Double-phase conductors in which ionic conductors are mixed with electron conductors can also be used for the same application.

US Patent No. 4,793,904 to Mazaneck et al. Discloses an ion transfer membrane coated on both sides with an electrically conductive layer. The oxygen containing gas is in contact with one side of the membrane. Oxygen ions are transported through the membrane to the other side where the ions react with methane or similar hydrocarbons to form syngas. Electrons emitted by oxygen ions can be used to flow from the conducting layer to the outside line and generate electricity.

In mixed conductor morphology, the membrane has the power to selectively transfer oxygen ions and electrons. It is not necessary to provide an external electric field for the removal of electrons emitted by oxygen ions. US Patent 5,306,411 to Mazaneck et al. Discloses the application of mixed conductor and double phase conductor membranes. The membrane consists of either a "single phase" mixed metal oxide having a perovskite structure with ionic and electronic conductivity or a multiphase mixture of an electronic conductive phase and an ion conductive phase. Oxygen ion transfer is disclosed to be useful for forming syngas and for correcting flue gases such as nitrogen oxides and sulfur oxides.

US Pat. No. 5,516,359 to Kang et al. Discloses a ceramic ion transport membrane integrated into a high temperature process that is effectively used for the operation of the membrane and the high temperature process. The hot compressed air is in contact with the oxygen-selective ion transport membrane and a portion of the oxygen contained in the air is delivered through the membrane and removed as product gas. Oxygen-depleted residual gas is combined with the gaseous fuel and reacted to produce hot gases that are typically useful for driving turbines that drive air compressors and generators for generation of electric forces.

However, there remains a need for a process for integrating ion transfer reactors with more efficient solid oxide fuel cells that require the generation of one or more product gases and electrical forces to achieve efficiency improvements.

It is an object of the present invention to provide a process for generating an electrical force and one or more product gases containing a single or a combination of oxygen, nitrogen, and carbon dioxide.

Another object of the present invention is to allow such a process to efficiently integrate solid oxide fuel cells into an ion transfer reactor. This object is aided by the fact that solid oxide fuel cells and oxygen ion transport membranes have similar operating temperatures.

Another object of the present invention is to use the flow out of the solid oxide fuel cell as the feed flow and the flow out of the holding surface and optionally the flow out of the permeate side of the oxygen-selective ion transfer membrane driving the turbine.

Another object of the present invention is to heat the feed gas directed to the cathode side of the oxygen transfer separator to the membrane operating temperature, using heat generated on the anode side of the fuel cell as a result of inefficient conversion of chemical energy into electrical energy. .

Another object of the present invention is to use the anode side of the fuel cell in series with the anode side of the reactively washed ion transfer membrane and add excess fuel to the anode flow of the fuel cell to use as a reactant in the purge flow. This increases the fuel cell energy conversion efficiency.

1 is a schematic diagram showing a solid oxide fuel cell integrated into a ceramic membrane ion transfer reactor according to the present invention.

2 is a schematic diagram showing an integrated system for co-production of power and oxygen.

Figure 3 is a schematic diagram showing an integrated system for the coexistence of oxygen and steam useful for power and coal vaporization.

4 is a schematic diagram showing an integrated system for coexistence of power and nitrogen.

5 is a schematic diagram showing an integrated system for coexistence of power, oxygen, and nitrogen.

6 is a schematic diagram showing an integrated system for coexistence of power, oxygen, and nitrogen.

7 is a schematic diagram showing an integrated system for the production of oxygen-free nitrogen inevitably.

The present invention consists of a process for generating electrical force and one or more product gases from an oxygen containing gas and a gaseous fuel. The solid oxide fuel cell is provided to have a first cathode or retention surface and a first anode or transmission surface. The first ion transfer reactor is located therein with an oxygen selective ion transfer membrane and the membrane has a second cathode or retention surface and a second anode or transmission surface. The oxygen containing gas is in contact with the first cathode surface and the gaseous fuel is in contact with the first anode surface causing the first oxygen portion to be transferred as oxygen ions from the first cathode surface to the first anode surface. Oxygen ions react with the gaseous fuel and generate an electron stream that is recovered as heat and electric force. Retention gas with residual oxygen is directed from the first negative electrode face of the solid oxide fuel cell to the second negative electrode face of the first ion transfer reactor, causing the second oxygen portion to be transferred through the ceramic membrane to the second positive electrode face. At least one product gas is recovered from the first and second anode surfaces and cathode surfaces, respectively.

In a preferred embodiment, the oxygen containing gas is air and compressed before contacting the first cathode surface. Oxygen is recovered from the second anode surface. A recovery heat exchanger transfers heat from the exothermic reaction product to the upstream of the first gaseous fuel of the oxygen containing gas and the solid oxide fuel cell.

In another preferred embodiment the heat generated in the fuel cell supplies at least a portion of the energy required to heat the air stream to the temperature at which the oxygen transfer membrane operates as a result of insufficient conversion of chemical energy into electrical energy in the anodic reaction. do. The vapor is used as a sweep gas for the second anode side and the second anode side permeate consists of a mixture of steam and oxygen used for coal vaporization. The cleaning gas is in contact with the second anode surface and the nitrogen gas containing low oxygen is recovered as the product gas.

In another preferred embodiment the reaction product produced at the anode side of the fuel cell is used to clean the anode of the oxygen transfer separator. A second reactively washed ion transfer reactor is located between the solid oxide fuel cell and the first ion transfer reactor.

In a preferred embodiment the fuel required in the reactively washed oxygen transfer reactor is added to the fuel supply to the anode side of the fuel cell and the fuel cell and the ion transfer reactors are placed in series to increase the efficiency of the fuel cell. Let's do it. Either of the electric force generated by the nitrogen generating gas or the solid oxide fuel cell under pressure is used to drive a compressor that compresses the oxygen containing gas.

The present invention can be accomplished by integrating a solid oxide fuel cell into a ceramic membrane ion transfer reactor. Preferably, the turbine is operated with one or more flows exiting the integrated system. Compressed air is conveyed to a solid oxide fuel cell in which a first portion of oxygen contained in the air is passed through a ceramic membrane to generate combustion products and electricity and exothermicly reacts with the fuel gas. The reduced oxygen-containing retention flow is discharged from the cathode of the solid oxide fuel cell to the cathode of the ion transfer reactor having an oxygen selective ion transfer membrane. The second portion of oxygen contained in the air is delivered through an oxygen selective ion transport membrane and can be recovered as product gas or used in a downstream reaction. The retentate from the ion transfer membrane may still contain sufficient oxygen even while oxygen is depleted so that in some embodiments it is mixed with gaseous fuel and burned to produce hot gases for driving the turbine. Optionally, nitrogen is recovered from the oxygen depletion stream.

1 schematically shows a process for integrating a solid oxide fuel cell 10 and a first ion transfer reactor 11 according to the invention. The solid oxide fuel cell 10 has a ceramic film 12 that divides the solid oxide fuel cell 10 into a first cathode surface 14 and a first anode surface 16.

The ceramic film 12 is oxygen-selective and transfers oxygen ions from the first cathode surface 14 to the first anode surface 16. Suitable material for the ceramic film 12 is yttria-stabilized zirconia. The porous air electrode 18 substantially covers all of the first cathode surface 14. Suitable material for the air electrode 18 is lanthanum manganite doped with strontium. The first interconnect portion 22 is not coated with the air electrode 18 and is electrically connected to the load 24. Oxygen ions are transported through the ceramic membrane 12 to the first anode surface 16 coated with the porous fuel electrode 26 except for the electrical interconnect portion. The fuel electrode 26 is made of a material that effectively minimizes losses due to polarization and is stable even at decreasing air pressures such as nickel-zirconia cermete.

Oxygen-containing gas supply 28 is conveyed to the first cathode surface 14 and gaseous fuel 30 is conveyed to the first anode surface.

Oxygen-containing gas supply 28 is typically air and the fuel cell at a temperature slightly below the operating temperature of the fuel cell (typically below 200-700 ° C.) to operate as a heat absorption reservoir for heat generated by the fuel cell reaction. Is transported to the cathode side. The operating temperature of the solid oxide fuel cell 10 is typically at least 500 ° C. and preferably in the range of about 700-1000 ° C. Oxygen molecules in the supply air dissociate into elemental oxygen as soon as they come into contact with the air electrode 18. "Elemental oxygen" refers to oxygen that is not bonded to other elements of the periodic table. Typically the term biatomic form, or the term elemental oxygen, as used herein, includes a single oxygen atom, ozone consisting of triatoms, and other forms not bound to other elements. Air is suitable as oxygen-containing gas supply 28.

The oxygen-containing gas supply 28 is compressed by the compressor 32 to a pressure of 30-300 psia, more preferably 100-230 psia. The compressed oxygen-containing gas supply is heated to a temperature of about 300-800 ° C., preferably about 500-700 ° C., and conveyed to the first cathode surface 14 as much as possible. The final heating of the feed air to the fuel cell and oxygen transfer membrane operating temperature takes place in the fuel cell by the chemical energy portion of the bipolar reaction which is released as heat without being converted into electrical energy and in turn the heat It is delivered to raise the temperature of the feed stream to the required level.

The gaseous fuel 30 is any one or combination of gases having a component exothermic with elemental oxygen. The reacting component may be natural gas or light hydrocarbons, methane, carbon monoxide or syngas ("syngas"). Syngas is a mixture of hydrogen and carbon monoxide with a molar ratio of H ₂ / CO of about 0.6-6. Another fuel gas component that may be undesirable in a fuel cell is an unreacted diluent gas such as nitrogen, carbon dioxide or steam.

The gaseous fuel 30 is preheated to a temperature of about 300-900 ° C. and introduced into the first anode surface 16. The reaction components of the gaseous fuel 30 exothermicly react with elemental oxygen. Electrons 34 released by the oxygen ions provide electrical force to the load 24.

A portion of the oxygen contained in the oxygen containing gas supply 28 is consumed by the reaction at the first anode surface 16. Retention stream 38 with reduced oxygen content leads to a second cathode surface 40 that is part of the first ion transfer reactor 11.

The first ion transfer reactor 11 has an oxygen-selective ion transfer membrane that separates the first ion transfer reactor 11 into a second cathode surface 40 and a second anode surface 50. The term "oxygen-selective" means that oxygen ions are selective across the oxygen-selective ion transport membrane 44 from the second cathode surface 40 to the second anode surface 50 relative to other elements and their ions. Means to be delivered. The oxygen-selective ion transfer membrane 44 is made of an inorganic oxide typed with calcium- or yttrium-stabilized zirconia. At elevated temperatures, generally above 400 ° C., the oxygen-selective ion transfer membrane 44 contains a mobile oxygen-ion space that supplies a conducting region for the selective transfer of oxygen ions through the membrane. Delivery through the membrane is driven by the ratio of the partial pressure of oxygen (P _o2 ) on both sides of the membrane. O ^2- ions flow from the side with high _PO to the side with low _PO . Ionization of O ₂ to O ^2- to the second taking place at the cathode side 40, ions are transferred to the second anode side 50, which may be recovered as product gas is O _2.

Oxygen-selective ion transfer membrane 44 is formed of either a dense mixed wall solid oxide or a biphasic conductor, or optionally a mixed solid oxide or biphasic conductor in the form of a thin film that supports a porous substrate. The oxygen-selective ion transfer membrane 44 has a nominal thickness of 5000 microns or less and is preferably 1000 microns or less.

When the difference in chemical potential caused by the ratio of oxygen partial pressure is maintained across the surface of the ion transport membrane, the oxygen-selective ion transport membrane 44 within the temperature range of about 450-1200 ° C. causes oxygen ions at a prevailing partial pressure. And pass electrons. Oxygen ion conductivity typically ranges from 0.01-100 S / Cm and S (“Siemens”) is the inverse of ohms (1 / Ω). Suitable materials for oxygen-selective ion transfer membranes consist of perovskite and biphasic metal-metal oxide bonds as listed in Table 2 of US Pat. No. 5,733,435. See the materials disclosed in US Pat. No. 5,702,999 to Mazaneck and 5,712,220 to Callaran et al. Materials with high ionic conductivity (at least 0.5 at 900 ° C., preferably 1 S / Cm) are suitable for the membrane 44 because the driving force for oxygen transfer is typically small (<10 ⁰ ). Suitable materials are mixtures of lanthanum, strontium and cobalt oxides.

In embodiments made of perovskite material, such as the material of a dense membrane layer, optionally the porous catalyst layer is an oxygen-selective ion transport membrane to enhance oxygen surface exchange in chemical reactions on the surface. It is added to one or both sides of (44). Optionally, the surface layer of the oxygen-selective ion transfer membrane 44 may be doped with, for example, cobalt to enhance surface exchange movement.

The first ion transfer reactor 11 is operated at a sufficiently elevated temperature to facilitate oxygen transfer through the oxygen-selective ion transfer membrane 44. The operating temperature is in the range of at least 400 ° C., preferably about 400-1200 ° C. and optimally in the range of about 400-1000 ° C.

On a volume basis, about 30-60% of the oxygen retained in the reduced oxygen gas feed output is delivered through the oxygen-selective ion transfer membrane 44 and recovered to the oxygen product gas 52. The percentage of oxygen that can be recovered depends on the respective partial pressures of oxygen at the second cathode surface 40 and the second anode surface 50. The percentage of oxygen recovered can be increased by reducing the oxygen partial pressure by the use of a sweep gas or vacuum pumping on the second anode surface.

Purge gases are oxygen removal gases such as natural gas, methane, methanol, ethanol and hydrogen. Sweep gas is a non-reactive gas that reduces the oxygen partial pressure. Suitable sweep gases include carbon dioxide and steam.

Optionally, the oxygen depleted retention flow 54 may be expanded directly within the turbine 62 or first delivered to the combustor 56 to react with the fuel 58 in the second gaseous state to generate turbine power 64. Can be. Combustion product 60 is a low oxygen containing hot gas that can be used to drive turbine 62 to generate turbine shaft power 64.

The efficiency of the process shown in FIG. 1 can be improved by the arrangement schematically shown in FIG. Recovery heat exchanger 66 receives heat released from elevated temperature gases such as product gas 52, combustion product 68 of solid oxide fuel cell 10, and combustion product 60 of combustor 58. Recover. Optionally, oxygen-depleted output 54 bypasses combustor 56 and dissipates heat to recovery heat exchanger 66. Heat is used to raise the temperature of the oxygen-containing gas supply 28 and the gaseous fuel 30.

Combustion product 68 is released after recovery of waste heat, as shown in FIG. Optionally, the combustion product 68 is led to the second anode surface 50 as a sweep gas as shown by the dashed line with arrow 68a to increase oxygen transfer and recovery. In this optional embodiment, the product gas 52 contains oxygen, water, and carbon dioxide. After condensation with water, low purity oxygen, which is diluted by carbon dioxide, is recovered. If desired, the oxygen and carbon dioxide generating gases can be separated by downstream swing adsorption or downstream processes such as polymer membranes.

Reactive washing equipment is disclosed in US Pat. Appl. No. 08 / 567,699 and European Patent No. 778,069, “Reaction Washing for Solid Electrolyte Membrane Gas Separation,” filed December 5, 1995. Suitable configurations for ion transfer modules using reaction washes are disclosed in US Pat. Appl. No. 08 / 848,204, "Solid Electrolyte Ion Conductor Reactor Design," filed April 29,1997.

Oxygen-depleted retentate in FIG. 2 is discharged to water containing 6-12% of the residual oxygen on a volume basis and dissipated heat to recovery heat exchanger 66, or optionally oxygen-depleted retentate. A portion 70 'or all of it is expanded in turbine 62 to recover power.

Since the oxygen depleted retentate 54 contains some residual oxygen, the combustor 56 can be inserted into the upstream of the turbine 62 and the oxygen depleted retentate is inlet of the turbine 62. In order to raise the temperature to between 1100-1500 ° C., it may react with the fuel 58 in the second gas phase to increase the production power and the thermodynamic efficiency of the system.

If the combustor 56 is missing or the extended flow 60 is at a too low temperature, the energy required to maintain the operation of the integrated system shown in FIG. 2 is supplied by the heat generated within the solid oxide fuel cell 10. The amount of generated heat depends on the efficiency of the solid oxide fuel cell 10 in converting chemical energy into electrical energy. This efficiency is such that if the heat generated by the solid oxide fuel cell 10 is inadequate, a large portion of the heat contained in the flow 54 may preheat the oxygen containing gas supply 28 and the gaseous fuel 30. It defines, in turn, the portion 70 'of the depleted retention flow 54 that can be expanded in the turbine 62 because it must be used in the recovery heat exchanger 66.

In an alternative embodiment, the recovery heat exchanger 66 is provided to a combustor (not shown) located upstream of the solid oxide fuel cell 10 for preheating the oxygen containing gas supply 28 and the gaseous fuel 30. Is replaced by.

3 schematically illustrates the application of an integrated system for supplying oxygen and steam to a coal vaporizer. Coal vaporizers typically require steam and oxygen at a molar ratio of about 1: 2 and elevated pressure, as disclosed in US Patent Application No. 08 / 972,412, filed November 18,1997.

In this embodiment, the air stream 28, the fuel stream 30, and the combustion product stream 68 from the fuel cell 10 are similar to that of FIG. 2. In FIG. 3, the retention flow 54 of the module 11 passes directly through the heat exchanger 66 and / or the combustor 56 ′ and the turbine 62 ′. The second anode surface 50 of the module 11 allows steam 72 to increase oxygen transfer through the oxygen-selective ion transfer membrane 44 by lowering the average oxygen partial pressure on the second anode surface 50. Is swept The advantages of steam sweeping are disclosed in US patent application Ser. No. 08 / 972,020, filed November 18,1997.

Vapor 72 is part of the process loop 73 that is integrated into the fuel cell / ion transfer module system. The water 74 supplied is pumped up to the pressure required by the pump 76, typically about 150-600 psia, and vaporized and superheated as in the recovery heat exchanger 66 to produce steam 72. do. Permeate stream 78 contains a mixture of residual oxygen and vapor. In the first embodiment the stream 78 is injected directly into the coal vaporizer 80 (although it appears to be a flow 102 but there is no addition of the stream 100 'as described below).

In a second embodiment, the stream 78 is divided into a first portion 82 injected into the coal vaporizer 80 and a second portion 84 extending in the turbine 63, cooled and conveyed to the condenser 86. . Most of the steam is condensed in condenser 86 and condenser output 88 is a mixture of liquid water and water saturated oxygen. Water is separated from the mixture in separator 90 and recycled water 92 is mixed with make-up water 74.

Water saturated oxygen removed from separator 90 is cooled in cooler 96 and compressed in compressor 98. Compressed stream 100 is reheated to heated stream 100 ′ by passing through a recovery heat exchanger and mixed with first permeate flow portion 82 to create flow 102. By adjusting the ratio of the compressed stream to replenish the first portion 82 and the stream 102, the desired ratio of vapor to oxygen of the coal vaporizer 80 is obtained.

The advantages of the system outlined in Figure 3 for separation generation and injection of steam and oxygen into a coal vaporizer include the reduction of the required ion transport membrane area and the savings in power required to compress oxygen. have. Better control of the steam to oxygen ratio is achieved by mixing the vapor and oxygen containing stream with the second high oxygen containing stream. Using steam as the sweep gas allows to operate the cathode side of the fuel cell ion transport membrane at a pressure lower than the vaporizer pressure, while saving oxygen compression power.

Optionally, a condenser (not shown) can be used to remove water from the output 78 to obtain a low vapor to oxygen ratio. However, this choice consumes a large amount of energy contained in the portion of the output 78 to be condensed, reducing the efficiency of the system.

4 shows an integrated system with a solid oxide fuel cell 10 and a first ion transfer reactor 11 useful for coexistence of power and nitrogen. The oxygen containing feed gas 28 is typically air and is compressed by the compressor 32 at a pressure of about 45-165 psia. The compressed air is then heated to a temperature of about 200-700 ° C. by the recovery heat exchanger and introduced into the first cathode surface 14 of the fuel cell 10. On a volume basis, about 60-70% of the oxygen contained in the oxygen-containing gas supply 28 passes through the ceramic membrane 12 and exothermicly reacts with the gaseous fuel 30. By maintaining a relatively high pressure on the first cathode surface 14, a relatively high oxygen partial pressure is maintained to allow a significant volume fraction of oxygen to be transferred through the ceramic membrane 12 and to achieve reasonable conversion efficiency. Due to the significant exothermic reaction occurring at the first anode surface 16, additional cooling may be required to avoid excessive temperature rise.

Retentate 38 with reduced oxygen content is conveyed to the first ion transfer reactor 11 to complete oxygen removal from the cathode side. Oxygen is delivered through the oxygen-selective ion transport membrane 44 and exothermicly reacts with the gaseous fuel 30 'at the second anode surface 50. Heat from this exothermic reaction is absorbed into the heating part 39 by the temperature rise of the cathode surface supply flow 38 '. Because of this, the flow 38 is cooled in the heat exchanger 66 or additional cooler 66 '. Retention stream 54 contains about 10 ppm of oxygen and may be carried at a pressure such as high pressure nitrogen product 104 after removal of useful heat by recovery heat exchanger 66. Optionally, at least a portion of the oxygen depleted stream 54 is expanded in turbine 62 and recovered as low pressure nitrogen product 106.

The first portion of the gaseous fuel 30 is carried to the first anode surface 16 of the solid oxide fuel cell 10. The second portion 30 ′ of the gaseous fuel 30 may be conveyed directly to the second anode surface 50 of the first ion transfer reactor 11. Preferably, the combustion product 68 is bonded at the contact 108 with the second portion of the gaseous fuel 30 to clean the second anode surface 50 with a diluent. Most preferably, all gaseous fuel 30 passes through the first anode surface 16 to increase the average fuel partial pressure at the anode of the solid oxide fuel cell 10 such that a high fuel partial pressure is applied to the fuel cell anode. The efficiency of the fuel cell is maximized by increasing the reaction rate in the reactor and thus minimizing the polarization loss.

Permeate gas 52 is substantially water vapor and carbon dioxide since nitrogen is excluded from the anodic reaction, except for the minute amount contained in the fuel. If desired, carbon dioxide product 109 may be recovered after condensation from water.

The system shown schematically in FIG. 4 generates a significant amount of excess heat since all the oxygen contained in the oxygen-containing gas supply 28 exothermicly reacts with the gaseous fuel 30. In a compact system this heat can be used to generate steam for export from the system. In large systems, excess heat can be used to generate additional power through a faint Rankine cycle. In the Rankine cycle, excess heat is directed to the boiler where the heat turns water into superheated steam. The steam expands with low pressure steam and drives the turbine to generate axial power. The heat is then removed in the condenser and the steam is reversed to the saturated liquid low pressure. The pump returns the pressure to the next boiler pressure. Heat for Rankine cycle 110 is preferably removed from flow 38 and / or 54.

5 shows a system for the coexistence of nitrogen and oxygen. The second ion transfer reactor 112 is located between the solid oxide fuel cell 10 and the first ion transfer reactor 11. The oxygen containing gas supply 28 is typically air, compressed by a compressor 32 to a pressure of 100-300 psia and heated by a recovery heat exchanger 66 to a temperature of about 300-800 ° C. The heated oxygen containing gas supply 28 is conveyed to the first cathode surface 14. On a volume basis, about 20-25% of the oxygen contained in the oxygen-containing gas supply 28 is transferred through the ceramic membrane 12 and carried to the load 24 for exothermic reaction with the gaseous fuel 30. And generates heat. The heat is effective to raise the temperature of the partially depleted retention stream 38 to a temperature in the range of about 900-1000 ° C.

The partially depleted oxygen gas stream 38 is at an effective temperature for oxygen separation in the second ion transfer reactor 112 and about 40-60% of the remaining oxygen is passed through the oxygen-selective ion transfer membrane 114. Delivered and recovered to oxygen product 116. The low oxygen containing retention stream 118 discharged from the second ion transfer reactor 112 releases heat to the heat exchanger 120. The released heat can be used for external Rankine power cycles and carried to recovery heat exchanger 66 or released as waste to compensate for the lack of heat in other parts of the system. A low oxygen containing stream 122 of reduced temperature (typically approximating 300-700 ° C.) is introduced into the second cathode surface 40 of the first ion transfer reactor 11. Typically, the oxygen content in the feed gas directed to the second cathode surface 40 of the first ion transfer reactor 11 is 2-7% by volume and is a sweep gas (suitable source consisting of combustion products 52). Third anode of second ion transfer reactor 112 to increase the driving force for oxygen transfer through oxygen-selective ion transfer membrane 114 by reducing the oxygen partial pressure at the third anode surface. It depends on whether it is introduced into face 124. If a sweep gas is used a lower value is obtained. Remaining oxygen is delivered through the oxygen-selective ion transfer membrane 44 and a mixture of fuel and combustion product 60 when gaseous fuel 30 or all fuel is introduced into the anode of fuel cell 10. And exothermic reaction at the anode surface 50 of the first ion transfer reactor (11). Retention oxygen depleted gas stream 54 exiting cathode surface 40 typically has an oxygen content of less than 10 parts / million.

As described above, the oxygen depleted gas stream 54 may be recovered to the high pressure nitrogen product 104 and after the stream 54 'is expanded within the powered gas turbine 62 or a combination thereof. May be recovered as low pressure nitrogen product 106.

The product gas 52 from the second anode surface 50 may be cooled to recover carbon dioxide 109 and water vapor. Optionally, product gas 52 may be conveyed to the anode side 124 of second ion transfer reactor 112. The permeate stream 116 in this case comprises a mixture of carbon dioxide, oxygen, and water vapor. If water vapor is removed, such as condensation, the gas will contain about 75-92% oxygen by volume. Pure oxygen can be obtained after separation and recovery of carbon dioxide and further drying.

The advantages of the invention mentioned herein will become more apparent from the following examples.

Example 1

6 shows a solid oxide fuel cell 10, a first ion transfer reactor 11 to co-generate an electric force against a load 24, oxygen, high pressure nitrogen 104 and low pressure nitrogen 106 as product gas 52. ) And a system incorporating the second ion transfer reactor 112 is shown schematically. Nitrogen product flow is assigned so that the power generated by the gas turbine 138 is sufficient to drive the air compressor 32 only.

The oxygen-containing gas supply 28, which is air, is compressed by the compressor 32 to a pressure of about 155 psia and is preheated in the recovery heat exchanger 66 before being conveyed to the first anode surface 14. There it is further heated to a temperature of about 950 ° C. because of the heat generated by the exothermic reaction occurring at the first anode surface 16. The solid oxide fuel cell 10 generates the recovered electrical force and is conveyed to a load 24 such as an external power grid after conditioning. The oxygen content of the partially depleted oxygen gas stream 38 is about 15% by volume.

Flow 38 is conveyed to the third cathode side 126 of the second ion transfer reactor 112. Oxygen corresponding to 12% of the oxygen contained in the feed air is delivered through the second oxygen-selective ion transfer membrane 114 such that the oxygen content of the retention stream 118 contains about 6% oxygen by volume. . Stream 118 is at an elevated temperature and releases heat in first superheater 128 to vapor stream 130. Flow 122 is at a reduced temperature and is introduced into second cathode surface 40. Here, the residual contained oxygen is removed by a reactive wash gas stream 68 which typically consists of fuel and combustion products coming from the first anode surface 16 of the first ion transfer reactor 11.

Oxygen-depleted stream 54 is a high-purity nitrogen stream and is expanded in turbine 138 that drives compressor 32 and first stream 134 that is recovered as high pressure nitrogen product 104 at contact 132. It is distributed or divided into two flows 136. The division between flows 136 and 134 is adequate so that the power delivered by turbine 138 meets the needs of compressor 32 when the turbine and compressor are mechanically connected. Flow in excess of the required flow is recovered to the high pressure nitrogen product 104. Waste heat from the expanding second stream 140 is recovered by the Rankine cycle 110 before being released from the system to the low pressure nitrogen stream 106.

The gaseous fuel 30 is heated in the recovery heat exchanger 66 and carried to the first anode surface 16. At the first anode surface 16, the gaseous fuel 30 exothermicly reacts with the delivered oxygen to produce electrical force and heat. The permeate stream 68 exiting the first anode surface 16 is intended to serve as a reaction wash stream to remove residual oxygen from the gas supply 122 containing excess unburned fuel and combustion products and partially oxygen deficient. It is introduced to the second anode surface 50 of the first ion transfer reactor 11. Permeate 144 from the second anode surface mainly contains combustion products (carbon dioxide and water vapor) and is released after recovering useful heat in recovery heat exchanger 66.

Optionally, the gaseous fuel 30 is compressed by a conventional element and the first anode surface 16 and the second anode surface 50 are then first and second cathode surfaces 14 and 40. It is operated at about the same pressure as If this is done the combustion products on the anode side can be carried at a pressure for recovery downstream of the increased carbon dioxide. Or, if no carbon dioxide coproduct is desired, is added to the second high pressure nitrogen stream 136 and expanded. This allows for the recovery of additional high pressure nitrogen as export of product 104 or additional power.

The third anode surface 124 is a sweep gas generated by pump 76 supplying water 74 to about 1000 psia by pump 76 and conveying it to boiler / heater 146 which converts it into steam 130 In the structure). The steam is then superheated in the second superheater 148 to a temperature sufficient to avoid moisture condensation during secondary expansion at a pressure of about 150 psia in the high pressure turbine 150.

The expanded vapor 130 is reheated in the first superheater 128 and used to clean the third anode surface 124. This improves oxygen recovery and increases the driving force for oxygen delivery. The above application to the steam circuit is described in more detail in US patent application Ser. No. 08 / 972,202.

Flow 78 is conveyed to low pressure steam turbine 152 at a pressure of about 150 psia with an oxygen partial pressure of about 20 psia. The expanded output 154 is at a pressure of 16 psia and is then cooled in the second superheater 148 to provide the heat required to overheat the steam 130. Cooled and expanded output stream 156 enters condenser 158 where most of the water contained condenses and enables recovery of oxygen as separator gas 52 from separator 90. The recycled water 92 is returned to a pressure of 1000 psia to complete the steam circuit by combining with the feed water to return to the pump 76.

Table 1 lists the input variables used to model the system shown in FIG.

parameter Value Instruction number of Fig. 6 Air flow 8.33 MMNCFH 28 Air compressor release pressure 155 psia (4 compression stages) 32 Air compressor efficiency 85% (insulation efficiency) 32 SOFC temperature 950 ℃ 10 SOFC efficiency 60% 10 Hot gas turbine inlet pressure 150 psia 138 Hot gas turbine inlet temperature 950 ℃ 138 Hot gas turbine exhaust pressure 16 psia 138 Inlet pressure of high pressure steam turbine 1,000 psia 150 Inlet temperature of high pressure steam turbine 430 ℃ 150 Inlet pressure of low pressure turbine 150 psia 152 Inlet temperature of low pressure steam turbine 900 ℃ 152 Exhaust pressure of low pressure steam turbine 16 psia 152 Steam condensing pressure 14.7 psia 158 Generated steam 303M lbs / hr 130

The calculated results for this system are shown in Table 2.

parameter Value Instruction number of Fig. 6 Oxygen product at 1 atmosphere 1,000 MNCFH 57% Rec. of O ₂ in Air 52 Nitrogen product at 9.86 atmospheres 2,990 MNCFH 104 Generated net power 98,100 KW 36 Heat required 711 MM BTU / hr system Heat rate 7,247 BTU / KW hr system Suitable heat rate for nitrogen compression 6,766 BTU / KW hr 66 Suitable heat speed for separating from 7KW / 1,000NCFH 6,344 BTU / KW hr 112

The results in Table 2 show a very attractive performance potential for the heat rates realized in spite of the relatively gentle peak temperature adopted in the cycle, while obtaining good oxygen recovery compared to conventional systems. As a further benefit, a significant amount of nitrogen contained in the air is carried at pressure.

Example 2

7 schematically shows another integrated system according to the invention. This system is particularly effective for the production of oxygen-free nitrogen, which is essentially oxygen, with the choice of the coexistence of oxygen and carbon dioxide. Using the parameters represented below in Table 3, the solid oxide fuel cell 10 is made to carry sufficient power to drive the air compressor 162.

The oxygen-containing gas supply 28, which is preferably air, is compressed by the air compressor 162 to a pressure of about 155 psia. The compressed air is then preheated to about 800 ° C. by the recovery heat exchanger 66 and introduced into the first cathode surface 14 of the solid oxide fuel cell. The gaseous fuel 30 enters the first anode surface 16 and exothermicly reacts with oxygen ions delivered through the ceramic membrane 12 and is a mixture of heat, electricity, and combustion products and gaseous fuel. Generate flow 68. The generated electric force is used to drive the electric motor 164 which drives the air compressor 162.

The partially oxygen depleted retention flow 38 exiting the solid oxide fuel cell 10 is at a temperature of about 950 ° C. On a volume basis, about 12% of the oxygen contained in the air is consumed by the reaction with the gaseous fuel 30 at the first anode surface 16. The partially oxygen depleted stream 38 is directed to the third cathode surface 126 of the second ion transfer reactor 112 and about 60% of the remaining oxygen on a volume basis is the second oxygen-selective ion transfer membrane. Passed through 114. The third anode surface 124 is a combustion product of the first anode surface 16, the second anode surface 50, or a combination of both to increase the removal and substantial recovery of a significant portion of the oxygen contained in the stream 38. Is swept The sweep gas reduces the oxygen partial pressure at the third anode surface 124 to increase the driving potential for oxygen recovery and / or oxygen delivery.

Retention flow 118 from third cathode surface 126 contains about 6% oxygen by volume. Stream 118 acts as a heat absorption reservoir 168 that cools in heat exchanger 166 and generates a reduced temperature stream 122 to absorb the heat of reaction generated by the downstream flow in first ion transfer reactor 11. do. The heat released from the low oxygen containing retention stream 118 in the heat exchanger 166 may be used to raise the temperature of the flow 170 for export or other use.

The reduced temperature flow 122 is conveyed to the second cathode surface 40 and the remainder of the oxygen contained in the second cathode surface 40 is transferred through the oxygen-selective ion transport membrane 44 and the second anode At face 50, it reacts with the gaseous fuel contained in the gaseous fuel / combustion mixture 68. Oxygen-depleted gas stream 54 removed from the second cathode surface 40 may contain up to 10 ppm of oxygen and may be conveyed to the high pressure nitrogen product 104 after recovery of useful heat. The gaseous fuel 30 is preheated in the recovery heat exchanger 66 and transported to the first anode surface 16 and reacts with oxygen transferred from the first cathode surface 14 through the ceramic membrane 12. Since the gaseous fuel 30 also contains the fuel required in the first oxygen transfer reactor 11, the average partial pressure of the gaseous fuel in the solid oxide fuel cell 10 rises to increase efficiency. Can be. The outgoing permeate stream 68 contains a gaseous fuel that is diluted by the combustion products and transfers first ions to remove oxygen delivered from the second cathode surface 40 through the ceramic membrane 44 by reaction washing. Enter the second anode surface 50 of the reactor 11. Outgoing permeate stream 144 contains combustion products (a mixture of water vapor and carbon dioxide) and is useful as a sweep gas for cleaning third anode surface 124 of second ion transfer reactor 112. Permeate stream 78 exiting second ion transfer reactor 112 contains a mixture of combustion products and oxygen. After recovering the useful waste heat in the recovery heat exchanger 66, the condenser 158 and separator 160 contain a low purity oxygen generating gas 52 containing about 75% of oxygen on a volume basis, where most of the impurities are carbon dioxide. ) Is used to recover. If necessary, carbon dioxide is removed by downstream processes and oxygen is recovered. Recycled water 92 is suitably discharged. If no oxygen or carbon dioxide is desired, flow 78 may also be discarded after recovering the useful heat in recovery heat exchanger 66. Table 3 shows the input parameters for the system shown schematically in FIG.

parameter Value Instruction number of Fig. 6 Air flow 126,000NCFH 28 Compressor discharge pressure 150 psia 162 Number of compression stages 3 162 Adiabatic compressor efficiency 85% 162 SOFC efficiency 60% 10 SOFC operating temperature 950 ℃ 10

The calculation results using the input parameters in Table 3 are tabulated in Table 4.

parameter Value Instruction number in FIG. Nitrogen products below 10 ppm 02 100,000 NCFH 104 Nitrogen product pressure 140 psia 104 Nitrogen recovery 100% 104 Potential oxygen by-products 6,120 NCFH contained in 75.9% purity 52 Byproduct pressure 14.7 psia 52 Oxygen recovery 61% 52 Potential flow for export 2,900 lbs / hr 170 Fuel Required 5,100 NCFH of natural gas 30

The advantage of the system shown in FIG. 7 is the availability of fuel diluents in the form of combustion products from the first ion transfer reactor 11 for cleaning the solid oxide fuel cell 10 and the second ion transfer reactor 112. availability). This allows for a high recovery of nitrogen and oxygen. Non-integrated separation systems (separate fuel cells or independent ion transfer membranes that provide power to the compressor) allow for air compression power and large energy costs for both systems due to cold cross-sectional temperature loss losses resulting in less efficient fuel utilization. Because of the larger fuel cells that require to provide the additional capital expenditure and capital and energy costs for separate air and fuel circuits.

Specific features of the invention are shown in one or more figures for convenience, as each feature may be combined with other features according to the invention. Alternative embodiments are contemplated by one of ordinary skill in the art and are intended to be included within the scope of the claims.

The present invention utilizes a solid oxide fuel cell and at least one ion transfer reactor to deliver oxygen-containing gas (typically air) to the cathode side of the solid oxide fuel cell and to deliver gaseous fuel to the anode side from the cathode side. The oxygen ions are exothermicly reacted at the anode side, and the waste heat is efficiently absorbed into the system by a recovery heat exchanger to efficiently integrate the ion transfer reactor with the solid oxide fuel cell, and the smoothing of the oxygen ions is achieved by washing the anode side. The system efficiency can be maximized and oxygen, carbon dioxide and nitrogen products can be separated and recovered.

Claims (10)

(a) providing a solid oxide fuel cell having a first cathode surface and a first anode surface; (b) providing a first ion transfer reactor having an oxygen-selective ion transfer membrane disposed therein, the oxygen-selective ion transfer membrane having a second cathode side and a second anode side; (c) contacting the first cathode surface with the oxygen-containing gas flow and contacting the first anode surface with the first gaseous fuel flow; (d) delivering a first oxygen portion of the oxygen-containing gas flow from the first cathode surface to the first anode surface; (e) reacting the first gaseous fuel flow with the first oxygen on the first anode surface and generating a flow of electrons from the first anode surface to the first cathode surface; (f) recovering the flow of electrons as an electric force; (g) directing the remainder of the oxygen-containing gas stream from the first cathode surface to the second cathode surface as a first retention flow; (h) contacting the first retention flow with the second cathode surface and transferring a second portion of oxygen from the second cathode surface to the second anode surface; And (i) recovering a gas flow as the product gas flow from at least one of the first cathode surface, the first anode surface, the second cathode surface, and the second anode surface; And a flow of generated gas from the electric and oxygen containing flow gas and the fuel flow in the first gaseous state. The method of claim 1 wherein the oxygen containing gas stream comprises air. The method of claim 2 wherein the air is compressed prior to contacting the first cathode surface. 4. The method of claim 3, wherein oxygen is recovered from the second anode surface as the product gas stream. 5. A method according to claim 4, characterized in that the holding gas flow coming from the second cathode surface is reacted with the fuel flow in the second gaseous state to generate combustion products. 6. The method of claim 5 wherein the combustion product is used to drive a turbine. 3. The method of claim 2, wherein the first heat exchanger is upstream of the air and the solid oxide fuel cell from at least one flow after a recovery heat exchanger contacts the flow with at least one of the first and second cathode and anode surfaces. Transferring heat to a gaseous fuel stream. 3. The method of claim 2, wherein the permeate gas stream exiting the second anode surface contains a mixture of steam and oxygen by sweeping the second anode surface with steam at elevated pressure. 10. The method of claim 8, wherein the ratio of vapor to oxygen in the permeate gas stream from the second anode surface is adjusted to a molar ratio effective for coal vaporization. The method of claim 9, wherein the adjusting step divides the permeate gas flow from the second anode surface into a first portion and a second portion, cools the second portion, condenses water from the second portion, Back compressing the gas remaining from the second portion to the pressure of the permeate gas stream and then recombining the first portion and the second portion.